This invention relates to a reactive pressure sensitive adhesive composition curable with heat or ionized radiation, and a sealing tape or sheet or molding by use thereof. More particularly, the present invention relates to a reactive pressure sensitive adhesive composition, which has initially adhesive force but generates bonding force though curing under melting by heat or curing as such by light, and to a sealing tape or sheet comprising the above reactive pressure sensitive adhesive layer having a thickness of about 10.sup.-5 to 10.sup.-2 m applied on a substrate surface or to a molding comprising the above reactive pressure sensitive adhesive which has any desired shape.
Pressure sensitive adhesive tape or sheet comprising the above pressure sensitive adhesive applied on a substrate surface has tackiness at normal temperature and can be plastered onto an objective material without any preliminary operation. Besides, it can be advantageously plastered again and therefore has been used in a variety of fields. However, what we call "pressure sensitive adhesive" has the drawback that it has generally weaker adhesive force as compared with adhesives. Also, since the tape is formed by coating a tape substrate with pressure sensitive adhesive, it cannot be plastered without a gap onto a site with a complicated shape, for example, a site with stepped difference, or a site which is recessed or protruded on account of thickness, hardness, firmness, etc. possessed by the substrate. Further the pressure sensitive adhesive tape involves therein a problem in water resistance, solvent resistance and heat resistance.
On the other hand, paints, adhesives, sealing materials are adaptable for complicated shapes, curved surfaces, holes, projections, stepped differences, gaps, etc. and also the curing reaction can be advantageously utilized in order to improve water resistance, solvent resistance and heat resistance of the pressure sensitive adhesive tape. However, these paints, adhesives and sealing materials require pretreatment such as mixing with a curing agent and they are ordinarily in the form of sol or paste contained in a solvent, and therefore many problems are involved in their handling, since some of them are difficult to be handled directly with hands or must be handled in a vessel due to their flowability. Also, care must be taken about contamination against the portions except for target portions to be applied due to flowing, sagging and splash during applications, and removal of the material once contaminated is extremely difficult and is frequently impossible.
Most of the sealing materials to be used in the vehicle body steps, the assembling steps or armoring steps of automobiles, ship, railroad vehicles, aircrafts, rockets, etc. are in a form of paste and those in a form of tape can be seen only in a part thereof. Tape-shaped sealing materials are difficult to have sufficient sealing effect at the site with a complicated shape, involving also a problem in water resistance and also weak adhesive force to be readily peeled off. However, since a very smooth surface can be formed, they have been used in applications where only appearance is made much of. On the other hand, paste-like sealing materials generally used frequently have excellent sealing effect and adhesive force, but cumbersome operation is required for making the appearance smooth and therefore they have been utilized at the sites in the inner portions which cannot be seen or which can be scarcely observed. However, in recent years, good appearance has been demanded by the users, particularly in the field of automobiles, even to the details which cannot be scarcely observed. For this reason, it has become necessary to have a sealing material endowed with both a beautiful appearance after application of the tape-shaped sealing material and sealing effect and adhesive force of the paste-like sealing material. In addition, for the paste-like sealing materials, a tool for exclusive use (usually gun) has been used in application. Accordingly, at narrow places where such gun cannot enter or working can be done with difficulty even if it can enter, not only workability is poor, but erroneous attachment of the sealing material onto places other than the intended areas will require enormous labor for wiping off and this cannot necessarily be removed completely.